This invention relates generally to the field of cataract surgery and more particularly to manipulation tools and irrigation sleeves used in phacoemulsification surgery.
The human eye in its simplest terms functions to provide vision by transmitting light through a clear outer portion called the cornea, and focusing the image by way of the lens onto the retina. The quality of the focused image depends on many factors including the size and shape of the eye, and the transparency of the cornea and lens.
When age or disease causes the lens to become less transparent, vision deteriorates because of the diminished light that can be transmitted to the retina. This deficiency in the lens of the eye is medically known as a cataract. An accepted treatment for this condition is surgical removal of the lens and replacement of the lens function by an artificial intraocular lens (IOL).
In the United States, the majority of cataractous lenses are removed by a surgical technique called phacoemulsification. A typical surgical handpiece suitable for phacoemulsification procedures consists of an ultrasonically driven handpiece, an attached cutting tip, and irrigating sleeve and an electronic control console. The handpiece assembly is attached to the control console by an electric cable and flexible tubings. Through the electric cable, the console varies the power level transmitted by the handpiece to the attached cutting tip and the flexible tubings supply irrigation fluid to and draw aspiration fluid from the eye through the handpiece assembly.
The operative part of the handpiece is a centrally located, hollow resonating bar or horn directly attached to a set of piezoelectric crystals. The crystals supply the required ultrasonic vibration needed to drive both the horn and the attached cutting tip during phacoemulsification and are controlled by the console. The crystal/horn assembly is suspended within the hollow body or shell of the handpiece by flexible mountings. The handpiece body terminates in a reduced diameter portion or nosecone at the body's distal end. The nosecone is externally threaded to accept the irrigation sleeve. Likewise, the horn bore is internally threaded at its distal end to receive the external threads of the cutting tip. The irrigation sleeve also has an internally threaded bore that is screwed onto the external threads of the nosecone. The cutting tip is adjusted so that the tip projects only a predetermined amount past the open end of the irrigating sleeve.
Recently, a modified phacoemulsification technique called “bimanual” phacoemulsification has been adopted by many surgeons. With the bimanual technique, the irrigation sleeve is removed from around the ultrasonically drive tip. This allows for the small tip to be inserted into the eye through a smaller incision. Irrigation fluid is supplied by a second irrigating tip. The second tip may include a manipulation tool. Additional information concerning traditional phacoemulsification and bimanual phacoemulsification is included in U.S. Patent Publication No. US 2003/0069594 A1. And in particular, Paragraphs [0036] through [0037] and FIGS. 6-8, which are incorporated herein by reference. As described in this reference, the second instrument does not use an outer silicone infusion sleeve. Rather the shaft of the manipulation tool is either hollow with irrigation ports, or solid with a separate hollow irrigating conduit containing irrigation ports. Without the outer silicone sleeve, sealing of the wound is minimal. This allows excessive irrigating fluid to escape out of the eye through the wound. Excessive wound leakage can cause shallowing of the anterior chamber, excessive turbulence and premature removal of the protective viscoelastic material. Excessive wound leakage can also cause over-hydration of the wound tissue, possibly resulting in edema.
Recently, it has been suggested that traditional one-handed phacoemulsification can be conducted through a relatively small incision by reducing the diameter of the phacoemulsification tip/sleeve. A second irrigation/aspiration tip, with or without an attached manipulation tool, may also be used to provide addition irrigation and aspiration. Such an arrangement minimizes wound leakage, thereby helping to avoid over-hydration of the wound, low intraocular pressure, excessive turbulence and premature removal of the viscoelastic material. The annular gap between the phaco tip and sleeve is used as an irrigation fluid pathway. Irrigation ports are provided on the sides of the sleeve to direct irrigating fluid out of and away from the aspiration port. Reducing the diameter of the infusion sleeve also reduces the amount of irrigation fluid that can enter the eye. Also, smaller diameter infusion sleeves are more likely to be compressed by the wound against the ultrasonically vibrating tip, thereby increasing the amount of heat.
Therefore, a need continues to exist for a method of using a smaller diameter irrigation sleeve that reduces the likelihood of excessive heat buildup and provides adequate irrigation during cataract surgery.